sure, the CEM will hopefully more advanced in CoD than in IL2. And so the chance to ruin your engine might bee much higher !
BUT, even i real it was not an unimportant feature for a Spitfire/Hurricane Pilot to be able to push his Merlin to 12lb/sq.in. boost (what was only possible with 100octane fuel without further damage to the engine).
It gave a good amount of addtional speed and climb at least till 10.000ft (in a lot of typical servers i would call that high alt
)
Here a sheet for a MerlinXII of the Spit II
http://www.spitfireperformance.com/spit2pnfs3.jpg
2-5min can be long in a fight
the Merlin III of the Mk.I Spits and Hurries dont differ much, they justr have a max 'normal' boost of 6 1/4 lb./sq.in. instead of 9 in the Merlin XII
increase boost with 100octane fuel
additional armour
CSPs
Radar
four points very important for the RAF to get its fightercommand ready to fight !